Abstract
Segregating human urine from wastewater may significantly contribute to diminish the nitrogen and phosphorous problem, considered to be one of the major planetary limits already exceeded. Application of urine diluted in water in agriculture contributes to both sides of the problem. On one hand, it allows reduction of nutrient discharges into receiving bodies, on the other, it reduces the need for reactive nitrogen and its energy demand. Advantages of application of urine inbermudagrass and macronutrients accumulation are shown in the previous paper. This paper presents the results of the evaluation of accumulation of micronutrients (B, Fe, Mn, Cu and Zn) in soil and in leaves of bermudagrass irrigated with different dilutions of human urine in water. The experiment was conducted in a greenhouse in a completely randomized design with six treatments consistingof six urine doses (0 - control, 5, 10, 15, 20 and 25 ml of urine per liter of water), with four replicates. As for concentrations in the leaves, there was a significant difference between treatments for all nutrients, with the largest accumulations, of B, Fe and Mn, 120 days after planting, observed in the 10 mL L-1 human urine dilution in water. There were significant differences among treatments in the soil layer 0-20 cm, for Fe, Mn and pH, concentrations as well as the levels of B and Mn in the soil layer 20-40 cm, and for B, Mn and pH between the layers analysed, in treatments 15, 20 and 25 ml L-1. Dilutions between 10 and 20 ml L-1 induced a greater accumulation of micronutrients in the plant tissue. The use of urine diluted in water provided adequate levels of micronutrients in the leaves in most of treatments, and it did not cause metal accumulation in the soil above the recommended levels for the bermudagrass cultivation. Key words: Cynodon dactylon, nutrient recycling, water reuse.
Highlights
The impoverishment of the soil, which increases the need for the application of fertilizer, is accentuated byAfr
For concentrations of B in plant tissue at the end of the experiment (Figure 1), the highest values (11.9 mgkg-1) were observed in samples that received dose of 10 ml L-1 of urine, greater than the 200% observed in the control treatment - T0 - (
Urine use caused the plants to show adequate levels of B in their tissues, which according to Wiecko (2006) is in the range of 6 to 30 mgkg-1, a value which was observed in all treatments except the control
Summary
The impoverishment of the soil, which increases the need for the application of fertilizer, is accentuated byAfr. Conventional sanitation systems because the nutrients excreted primarily in urine and the feces are mixed with water and other waste streams and discharged into water bodies. This final discharge causes a deficit of nutrients in the soil, but it presents environmental and sanitary risks. The main source of these nutrients in the domestic sewage is human urine (Tidåker et al, 2007), which could be collected at source and exploited in agriculture By this mean, other significant energy savings may be obtained as the the process of transforming inert nitrogen (N2) from the atmosphere, to reactive nitrogen (Nr) demand about 13 kWh kg-1 of Nitrogen
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